1. Field of the Invention
The present invention relates to a fluorescent endoscope system for simultaneously producing a reflected-light image depicted by reflected light with wavelengths in the visible spectrum and a fluorescence image depicted by infrared radiation.
2. Description of the Related Art
In recent years, an endoscope of which insertional part is inserted into a body cavity for the purpose of observing the alimentary canal extending from the esophagus through the stomach to the small and large intestines or the trachea extending to the lung, or if necessary, of conducting various kinds of treatments using therapeutic instruments inserted into a therapeutic instrument channel has been put to use. In particular, an electronic endoscope having an electronic imaging device such as a charge coupled device (CCD) has been widely adopted because an image can be displayed on a monitor and an operator of the endoscope is little fatigued with manipulation.
Recently a modality in which a fluorescent substance having an affinity for a lesion such as a carcinoma is administered to a subject to be examined in advance, excitation light for exciting the fluorescent substance is irradiated, and fluorescence emanating from the fluorescent substance is detected.
According to the modality, since intense fluorescence is radiated from a lesion, the presence of the lesion can be judged from the brightness of a fluorescence image. A system adopting the modality is, for example, a system, as disclosed in Japanese Unexamined Patent Publication No. 59-40830, for detecting fluorescence emanating from hematoporphyrin that is a fluorescent substance.
In the system disclosed in Japanese Unexamined Patent Publication No. 59-40830, control is provided that pulsed laser light for excitation and white light for normal observation can be irradiated selectively. Japanese Unexamined Patent Publication No. 7-59783 has disclosed a system enabling observation of fluorescent substances such as chlorin and pheophorbide. In the system disclosed in Japanese Unexamined Patent Publication No. 7-59783, light suitable for exciting a fluorescent substance and light suitable for normal light observation (white light) are irradiated while being switched by a rotary filter.
Prior methods for exciting fluorescent substances include irradiating light with relatively short wavelengths of about 405 nm. When light with the wavelengths is irradiated to a living tissue, the living tissue itself fluoresces. Unless an apparatus exhibiting high spectroscopic precision such as a spectrometer is employed, it is hard to distinguish self-fluorescence from fluorescence emanating from a fluorescent substance.
The transmittance of light with short wavelengths relative to a living tissue is so poor that a system using hematoporphyrin to be excited by light with short wavelengths may miss the presence of a substance fluorescing,in a deep subcutaneous region.
In the prior art, excitation light and white light are irradiated while being switched temporally. Consequently, during irradiation of excitation light, a fluorescence image alone can be produced. During irradiation of while light, a normal light image alone can be produced. There is a large difference in time between the fluorescence image and normal image.
The first object of the present invention is to provide a fluorescent endoscope system enabling observation of a fluorescent substance that is excited to fluoresce by means of light with wavelengths in an infrared spectrum exhibiting good transmittance relative to a living tissue, such as, an antibody labeled by indocyanine green, capable of nullifying the influence of self-fluorescence, and capable of preventing a lesion in a deep subcutaneous region from being missed.
The second object of the present invention is to provide a fluorescent endoscope system in which since a reflected-light image depicted by reflected light and a fluorescence image can be produced simultaneously, there is no difference in time between the images, which enables easy diagnose of a lesion, and of which endoscope can be oriented easily.
A fluorescent endoscope system comprises: an endoscope having an elongated insertional part capable of being inserted into a living body; a light source means for simultaneously irradiating excitation light with wavelengths in a first infrared spectrum, which causes a fluorescent substance to be administered to a living tissue to fluoresce, and light with wavelengths in the visible spectrum; a separating means for separating fluorescence with wavelengths in a second infrared spectrum including at least part of the wavelengths of the fluorescent substance and different from the first infrared spectrum, from light stemming from the living tissue; a first imaging means for forming an image depicted by the fluorescence separated by the separating means; and a second imaging means for forming an image depicted by light with wavelengths in the visible spectrum. Owing to these components, self-fluorescence can be cut off together with light with wavelengths in the infrared spectrum that are longer than the wavelengths of the self-fluorescence. Fluorescence observation of an object using a fluorescent substance that is characteristic of good transmittance and ready accumulation in a lesion, such as, an antibody labeled by indocyanine green can be carried out. Fluorescence emanating from a lesion in a deep subcutaneous region in which the fluorescent substance is accumulated can be observed but will not be missed.